On Thu, 08 Nov 2012 15:39:24 -0500, Terry Reedy wrote: [...] > test.py:21: UserWarning: 'bar': is not property. > assert looks(Foo).like(IFoo) > Traceback (most recent call last): > File "test.py", line 21, in > assert looks(Foo).like(IFoo) > AssertionError > ''' > > I view this check as an error. Properties are intended to be transparent > to the user. One use of properties is to make something that is not a > Mallard act like a Mallard. So this check breaks duck typing.
Properties and methods do not have the same interface: IFoo.bar # returns a computed property Foo.bar() # calls a method Since the interfaces are different, duck-typing will fail. It will actually fail in a potentially nasty way: x = Foo.bar # doesn't raise an exception, gives the method object # ... much later do_something_with(x) # blows up potentially far, far away -- Steven -- http://mail.python.org/mailman/listinfo/python-list
